2004 Denver Annual Meeting (November 7–10, 2004)

Paper No. 5
Presentation Time: 1:30 PM-5:30 PM


GORRING, Matthew L., Department of Earth and Environmental Studies, Montclair State University, Upper Montclair, NJ 07043, GATES, Alexander E., Department of Geological Sciences, Rutgers Univ, Newark, NJ 07102, VALENTINO, David W., Department of Earth Sciences, SUNY-Oswego, Oswego, NY 13126, SOLAR, Gary S., Department of Earth Sciences, SUNY College at Buffalo, 1300 Elmwood Avenue, Buffalo, NY 14222 and CHIARENZELLI, Jeffrey R., Department of Geology, State Univ of New York, Potsdam, NY 13676, gorringm@mail.montclair.edu

Large-scale, high-grade ductile shearing, migmatization, and the emplacement of a chemically diverse suite of granitoid plutons characterize the late- to post-Ottawan (<1030 to 925 Ma) geologic history of the northernmost New Jersey Highlands and the Hudson Highlands of New York. The ductile shear zones are large (0.5 to 2 km wide, 2-10 km long), subvertical to vertical, and all kinematic indicators consistently show dextral strike-slip deformation. Timing of deformation is broadly constrained to an upper limit of »1010 Ma based on the SHRIMP U-Pb zircon ages on crosscut metaplutonic rocks and a rough lower limit of »925 Ma based on hornblende 40Ar/39Ar age obtained from an undeformed, crosscutting granite pegmatite dike. At least four discrete granitoid suites were emplaced associated with this shearing event that range from A- and S-type granites to calc-alkaline, I-type gabrro and diorite. These are, in order of inferred or radiometric age: (1) the Sterling Forest Granite Sheets (not yet dated), the Mount Eve Granite (1020±4 Ma; Drake et al., 1991), the Canada Hill Granite (1010±6 Ma; Aleinikoff and Grauch, 1990), and the Lake Tiorati Metadiorite (1008±4 Ma). The Sterling Forest Granite Sheets consist of tabular bodies (5-200 m thick) of metaluminous to slightly peraluminous leucogranite (SiO2 »75%) with transitional I- and A-type trace element characteristics. The Mount Eve Granite consists of about thirty small stocks (0.2-5 km2) of metaluminous syenogranite to quartz monzonite with strong A-type chemical signatures (e.g., high Fe, Ba, Zr, Y, HFSE, REE). The Canada Hill Granite is a peraluminous biotite leucogranite with S-type chemical affinities (e.g., high Si, Al, K, low Fe, highly variable REE content) consisting of small stocks (0.1-1 km2) and sheets (~2-4 m thick) that intimately associated with surrounding migmatitic metapelitic gneisses. The Lake Tiorati Metadiorite consists of small stocks and sheets (max. 1.5 km2) of mafic rocks (47-51% SiO2) with strong I-type, calc-alkaline, continental arc chemical signatures (e.g., low Ti, HFSE). Dextral transcurrent shearing and granitoid emplacement is interpreted here to have resulted from a tectonic escape mechanism due to late- to post-Ottawan adjustments within the newly amalgamated Rodinian supercontinent.